Intermediate Example L; Synthesis of ethyl 2-chloro-4-methyl-1,3-thiazole-5-carboxylate (X-1): ethyl 2-oxo-4-methyl-3H-thiazole-5-carboxylate (0.57 g, 3.05 mmol) was mixed with phosphorus triclosan (5 mL) and heated to react for 18 hours at 120°C. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently concentrated under reduced pressure to remove excess phosphorous trichloride. Water (15 mL) was slowly added to the residue and stirred for 10 minutes. The aqueous phase was extracted with ether (3 x 15 mL), the organic phases were combined and dried over anhydrous magnesium sulfate. After filtration, the organic phase was concentrated under reduced pressure to give the crude product. The crude product was purified by column chromatography (ethyl acetate/hexane as eluent) to afford ethyl 2-chloro-4-methylthiazole-5-carboxylate as a white solid (0.54 g, 86% yield).1H NMR (400 MHz, CDCl3) δ 4.32 (q, J = 7.1 Hz, 2H), 2.68 (s, 3H), 1.35 (t, J = 7.1 Hz, 3H). 3H).
